الوهن العضلي الوبيل

Definition

Myasthenia gravis is antibody attack on muscle acetylcholine receptors, so muscles weaken with repeated use.

Symptoms

• Weakness that worsens with use and improves with rest, worse late in the day
• Ptosis and diplopia
• Difficulty chewing, swallowing and speaking
• Respiratory weakness when severe

Diagnosis

Serum antibodies, nerve conduction studies and chest imaging for the thymus.

Treatment

• Pyridostigmine 30–60 minutes before meals
• Steroids and immunosuppressants
• Thymectomy for some
• Crisis: IVIG or plasma exchange and respiratory support

Two crisis types

• Myasthenic: too little drug or infection; severe weakness
• Cholinergic: too much drug; weakness with salivation, sweating, diarrhoea, miosis

Nursing care

• Monitor vital capacity and swallowing
• Fixed dosing times and paced activity
• Avoid drugs that worsen weakness, such as aminoglycosides and some quinolones

Exam point

The most dangerous complication is respiratory weakness, monitored by vital capacity, not saturation alone.